초록 ▼

An improved nozzle for gas-assisted injection molding and a method of gas-assisted injection molding using the improved nozzle are provided. This improved nozzle employs a very simple design to vent the gas from the mold cavity once the plastic article has cooled sufficiently to be self supporting.

An improved nozzle for gas-assisted injection molding and a method of gas-assisted injection molding using the improved nozzle are provided. This improved nozzle employs a very simple design to vent the gas from the mold cavity once the plastic article has cooled sufficiently to be self supporting. In one especially preferred embodiment of this invention, the improved nozzle contains a separate plastic shut-off valve, a separate gas inlet passage with a check valve, and a separate gas venting passage containing a movable pin. Venting of the pressurized gas occurs by movement of the movable pin so that the pressurized gas can burst through the thin layer of plastic material covering the gas venting passage. The improved nozzle design and method allow for almost continuous operation with minimal operator attention to the nozzle.

대표청구항 ▼

A nozzle for use in a gas-assisted injection molding machine, said nozzle comprising: (1) a nozzle body having an upstream end for communication with an associated injection molding machine and a downstream end for communication with an associated mold containing at least one mold cavity, said nozzl

A nozzle for use in a gas-assisted injection molding machine, said nozzle comprising: (1) a nozzle body having an upstream end for communication with an associated injection molding machine and a downstream end for communication with an associated mold containing at least one mold cavity, said nozzle body including: (a) an axially extending plastic passageway for establishing a molten plastic flowpath; (b) a first valve chamber provided in the plastic passageway and in fluid communication therewith; (c) a gas entry passageway having a first end which intersects and communicates with the plastic passageway near the downstream end of the nozzle body, and a second end of said gas entry passageway terminates at a first location on the outer surface of the nozzle body; (d) a second valve chamber provided in the gas entry passageway and in fluid communication therewith; and (e) a gas exit passageway having a first end which intersects and communicates with the plastic passageway near the downstream end of the nozzle body and is in close proximity to the first end of the gas entry passageway and a second end of said gas exit passageway terminates at a second location on the outer surface of the nozzle body; wherein the first valve chamber is located between the upstream end of the nozzle body and first ends of both the gas entry passageway and the gas exit passageway: (2) A shut-off valve mounted in the first valve chamber for movement between a first position and a second position, wherein when the shut-off valve is in the first position the molten plastic flowpath is established between the upstream end and the downstream end of the nozzle body such that molten plastic can flow through the plastic passageway into the associated mold, and when the sut-off valve is in the second position the molten plastic flowpath is blocked; (3) a check valve mounted in the second valve chamber which allows gas to pass from the second end to the first end of the gas entry passageway and enter into the plastic passageway but prevents gas from passing from the first end to the second end of the gas entry passageway; and (4) a pin located in the gas exit passageway which is movable between a first position and a second position, wherein when the pin is in the first position and a second position, wherein the pin is in the first position gas and molten plastic in the plastic passageway cannot pass through the gas exit passageway, and when in the second position gas can pass through the gas exit passageway and thereby vent to atmosphere via the gas exit passageway.